1. Field of the Invention
The invention relates to brake fluid pressure control devices including a plurality of fluid pressure control valves that control fluid pressures in a plurality of brakes.
2. Description of Related Art
Japanese Laid-Open Patent Application No. 7-277175 discloses a brake fluid pressure control device including: (1) a control device mainly composed of a computer, (2) a pump that pressurizes operating fluid by means of motive power, (3) fluid pressure control valves that operate in accordance with control signals supplied from the control device and capable of controlling fluid pressures in brakes based on a fluid pressure in the pump, (4) pump shut-off valves provided between the fluid pressure control valves and the pump and that are switched in accordance with control signals supplied from the control device between a communication state where the fluid pressure control valves communicate with the pump and a shut-off state where the fluid pressure control valves are shut off from the pump, and (5) signal lines connecting the fluid pressure control valves to the control device and signal lines connecting the pump shut-off valves to the control device.
In this brake fluid pressure control device, the fluid pressure control valves are provided on the side of front wheels and on the side of rear wheels respectively. The pump shut-off valves are provided between the front-wheel-side fluid pressure control valves and the pump, and between the rear-wheel-side fluid pressure control valves and the pump respectively. If an abnormal condition arises either on the side of the front wheels or on the side of the rear wheels, the pump shut-off valves provided on the side experiencing the abnormal condition are switched to a shut-off state in accordance with control signals from the control device. Consequently, the fluid pressure control valves are shut off from the pump, and the brakes are operated by operating fluid in a master cylinder.
However, the aforementioned publication does not disclose a fail-safe system of such a brake fluid pressure control device, for example, as a countermeasure against cases where connectors for the signal lines are disconnected or incorrectly connected (where an abnormally connected condition arises) and where electric energy cannot be supplied to the fluid pressure control valves, the pump shut-off valves and the pump.